Because forex do not actually include bitcoin signals when trading bitcoin on forex apps. Instance! When you wants to trade forex you can get signals and indictors apps from google play store but no such for bitcoin?
There are platforms and brokers that have both crypto and Forex pairs now. In the recent past it wasn't possible. Innovation has proved consistently that change is a necessity for growth and advancement. In fact, in 2017 when I joined the crypto business one could only trade cryptos as a Spot. The Futures optiop wasn't there. It was enter one sold Bitcoin for altcoins or exchanged it for fiat at once. It was only a one-way traffic then to make profit. One could only buy and hodl, then wait for price to appreciate to sell off. It's different today as anyone can sell without even buying, just like what we've in Forex trading.
Talking about indicators, one could trade cryptos using the same indicators one trades forex with. It's just a matter of backtesting them to know which works well and with what parameters to set them to.